The object of the proposed research is to study the biochemistry of excitable membranes as it relates to structure, function, and biological assembly. The scope of the original proposal will be expanded to include mammalian muscle sarcolemma as well as nerve membrane. We will investigate the use of enzymatic iodination, and pyridoxal phosphate labelling in conjunction with SDS acrylamide gel electrophoresis as probes of the topologic arrangement of membrane proteins. Attempts will be made to develop a covalently-bound blocker of the chloride permeability site in the sarcolemma using draminostilbene derivatives; in labelled form these blockers could provide tags for membrane proteins associated with this permeability system.